A
halogen lamp, also known as a
tungsten halogen,
quartz-halogen or
quartz iodine lamp, is an
incandescent lamp that has a small amount of a
halogen such as
iodine or
bromine added. The combination of the halogen gas and the
tungsten filament produces a
halogen cycle chemical reaction which redeposits evaporated tungsten back onto the filament, increasing its life and maintaining the clarity of the envelope. Because of this, a halogen lamp can be operated at a higher temperature than a standard gas-filled lamp of similar power and operating life, producing light of a higher
luminous efficacy and
color temperature. The small size of halogen lamps permits their use in compact optical systems for projectors and illumination.